Preheat oven to 350.
Lightly coat four mini-loaf (2-cup) pans with cooking spray.
Place bananas and sugar in a mixing bowl and beat for 2-3 minutes.
Add butter, egg and vanilla extract, mixing well.
Scrap down bowl sides and add flour, cocoa powder, cinnamon, salt, baking soda, and nuts.
Mix to combine.
Fill pans about half full with batter.
Bake until firm in the center and a toothpick inserted comes out with a bit of crumb on it, 35-40 minutes. (Or use 16 muffin tins and bake 15-18 mintues, or a full-size loaf pan for 1 hour.)
Cool completely.
To freeze, warp in plastic and then foil and freeze up to one month.
